As with many things, vaulting has made me have to rethink my bonus hero strategy. And currently, I’m kind of at…I don’t know what my strategy is. 3*'s are easy, I have Strang3 and Thanos, because they are my favorite 3s to use and actually use them even when they’re not boosted. 5, I have Thanos, because, well, he’s my favorite comic book baddie and he’s pretty good. The problem now lies in 4* land. New characters are easy to come by, so I don’t want to pick them, but since older 4s are harder to come by, it’s kind of like, “What’s the point?”. Currently, I have Carol as my 4 sitting at 4/5/0, which makes me nervous about possibly, maybe getting my 2nd 4* BH and having it be a yellow Carol. So, ultimately, just looking for some input on what makes sense for other people when choosing your BH.
I have been choosing a single 4* at 12 covers, with a preference for older characters, and characters at 3/4/5 over ones at 5/2/5. Don’t have anyone at 4/4/4 
So far I have champed Thor, Ice Man, and Jean Grey (just today :D) in this way. Ant-Man is up next.
I have X-23 (Vaulted and Champed), Jean Grey (12 Covers 1 Power Maxed) and Quake (just because) Selected for 4’s
3’s are Hawkguy and all champions not in tokens
5 is Black Widow, ‘cuz ahe’s the Black Widowand she’;s the only 5 I use outside of trivial nodes
I choose my 4s based on those that don’t have a power maxed at 5. So right now is Spider Gwen.
My 3s I choose by 4 star rewards. So lazy cap at 218 to get his 223 reward. Then I’ll work on thanos at 181.
My 5s I just switch to whomever I just feel like at the moment. Only gotten a 5 once before.
5: Green Goblin. It was OML, but since his nerf, I’m just picking the hero with my favorite kit / that looks the most fun to play. I’ve got a fully champion’d 3* roster but not one champion 4*, so I feel like there’s some freedom in the 5* space. Sure, I should probably be trying to improve my 3/1/1 Thanos, but I actually want to play Goblin for fun. I feel like the fun part of this game gets lost with how tedious progression is.
4: Iceman. I really enjoy collecting additional blues for my 3/5/1 Iceman, so I have him favorited so that I can wallow in misery at the useless bonus heroes I collect. In all seriousness, though, I want to start my 4* transition with quality talent, as it were, and Iceman tops the list.
3: It was Hawkguy, who was 1/3/3 three days ago. Now that he’s championed and earned me a Legend Token (sigh, Mordo Black cover), I’m going to be targeting 3s based on their 4 champion rewards. I think maybe Cyclops until I get the next cover there. Should probably be Mystique, but I’m bitter because she’s level 182 and the next level will earn me yet another blue Iceman dupe.
I select the 4* Bonus Hero that I am closest to full covering. Right now its Peggy Carter for me, but the annoying thing is, every time I get a bonus pull of her, it’s blue, and I have a 5 in blue. Really annoying and frustrating as she is a 4/3/5.
5* Black Panther and Hawkeye. It was BP and GG but after I got that yellow cover a couple days ago, I switched to him Hawk. I’m at 2/1/2 with BP, 3/3/1 with GG and only 0/1/0.
4* Medusa, Coulson, Wasp. It was Medusa, Carol, and Wasp but I just got Carol to 4/5/3, so I moved to Coulson from her. Wasp is 5/4/3 but I’ve got 3 yellow covers in the cache. I really need a blue or black. I’ll champ her immediately. Medusa is 4/3/4. Moving along very well.
3* Steve Rogers, Storm, and Hawkguy. I’ve got Steve at lvl 253. I get his BH covers more than anybody’s. The rewards are so high, I just don’t think I can miss out on them. Storm is now at lvl 221. I’m trying to push her to get that T4or yellow cover. And Hawk is at 1/3/3. I just really want more Hawk covers.
5 Stars:
Thanos - Mine is 3 3 1, he’s strong, and he’ll be leaving Latest Tokens next… I have him as the only one to try and speed that up, cause I suspect a 5 Star being released with the GotG movie…
4 Stars:
Due to OCD Collection issues, any that I don’t have cover maxed that are vaulted:
Drax, Mr. Fantastic, The Punisher, War Machine
All are 1 or 2 covers away. I did have Winter Soldier there too, but my next Lazy Cap Champ level will give me the 13th cover, so I figured I’d marginally increase my odds for these others by taking him out.
3 Stars:
I have them all champed, so I’m going with the best ones that help PVE grinding:
Dr. Strange, Iron Fist, Thanos
5/3/2 here and my last 5 pulls have been red.
For 5*'s, I chose the first three released, Phoenix, OML, and Silver Surfer. OML is likely to get changed for Thano5. He’s caught up to my Phoenix (4 covers) rather quickly. For my 4*'s, I’m targeting one by one those closest to being fully covered. Right now, it’s my Hulkbuster at 4/4/4. For 3*'s, whoever is closest to a 4* I’m actually interested in.
5* Thanos
4* Spider-Gwen (12 covers)
I have 9 4*s to champ, so I don’t even think it matters at this point.
3* Wolverine
I have been using the 3* closest to 266. After Wolvie I will switch to any of the 3s that get covers from my 2 farm since most of them are at 220 and above.
I have bss and old man in 5 star land.
4’s I have Carol and wasp because I enjoy the synergy of them and neither is maxed or champed.
3’s are all champed except hawkguy. So I am going for the ones that give 4’s I want. So for now I have daken and ragnarok. Once they both get the 2nd cover for x-23 i will be able to champ her. Then i will move on to whoever rewards covers for my 11 to 12 cover 4 stars.
My roster is currently in the 3-4 transition – almost all my 3s are champed (except She-Hulk and the new Hawkeye) but none have even reached 200. Meanwhile, I have about 2/3rds of the 4s rostered but most of them are 3 covers or less, and even the ones beyond that point, I’m stopping them around 150-160 until I decide who to push.
In the 3s, I’m still focused on unlocking roster spots, so I favorite anyone who is 1-2 levels away from generating HPs. (So 169-170, 177-178, 185-186, etc.). I’ll also favorite anyone in the 181-182 range if I can use the cover I’d get at 183 (i.e. either already have the hero or expect to be able to open a roster spot soon enough to roster it).
In the 4s, three-pronged strategy: I’ll usually favorite a) whoever’s featured in the current/upcoming PvE event(s), b) all my 1-2 cover 4s, just to try to make them marginally less useless, and c) if I’m not too pinched on roster space, ONE 4* that I don’t have rostered (Iceman, currently). Once I either have all the 4s rostered or some of them reach champion status, I’ll re-evaluate.
For 5s, I don’t really care at this point. Right now I have BB set as my favorite… just because… but I’m kind of indifferent.